The 1860 collapse of the Pemberton Mill, a five-story brick factory located near the corner of Canal and Union streets in Lawrence, ranks as one of the worst industrial disasters in the Commonwealth’s history.

On the afternoon of Jan. 10, the mill buckled and crashed without warning, killing dozens of people instantly and trapping hundreds more under tons of rubble. Later that night, as rescuers frantically tried to free victims still alive under the debris, a fire broke out and ignited the piles of splintered wood and oil-soaked cotton bales and textiles at the site. One trapped man reportedly cut his own throat with a knife rather than be burned alive; he was eventually rescued, but later died from his injuries. In all, an estimated 145 workers perished and 166 were injured in the horrific collapse and ensuing conflagration.

“The largest number of workers who lost their lives were women, some as young as 15 and 16; most were Irish immigrants,” says history Prof. Robert Forrant, co-director of UMass Lowell’s Center for Family, Work & Community. “Industrial work in the 19th century was nasty, violent and physically demanding, and most factory owners knew that with fresh numbers of immigrants coming all the time, workers could literally be ‘used up’ and replaced.”

“The Pemberton Mill’s structural failure was preventable,” says civil engineering Asst. Prof. Tzu-Yang Yu. “The mill’s designer and chief architect, Captain Charles H. Bigelow, wanted to build the largest and most efficient mill in New England and made some mistakes in Pemberton’s design and construction. Some mistakes were due to lack of sufficient scientific and engineering knowledge, but some were simply due to ignorance and overconfidence.”

Forrant and Yu will be featured in an hourlong documentary about the mill tragedy that is being produced by Louise Sandberg of the Lawrence Public Library.

“The program, entitled ‘The Case against Captain Bigelow,’ will be aired on Lawrence television sometime this fall,” says Sandberg.

“I was interviewed for the documentary to help create context for the mill’s collapse and the nation’s rapid industrialization prior to the Civil War,” says Forrant.

He says Lawrence and Lowell were two of the most industrialized cities in the country at the time and mill construction was conducted with very little regard for worker health and safety.

“The drive to build Pemberton quickly resulted in corners being cut with the building materials, and then too many textile machines were packed into the mill space,” he says. “The result was a disaster waiting to happen. As for the collapse itself, it was well known that the materials used to manufacture the posts to hold up the floors were of poor quality. The inquest after the collapse made this clear.”

“My role as a structural engineer was to investigate the failure mechanism for the Pemberton Mill collapse,” says Yu. “I performed static and dynamic analyses to see what the internal force distribution looked like.”

He says there are three main causes that led to the total collapse of the mill: first, its structural system was inherently weak due to the mill’s excessively large windows and thin walls; second, its construction period was much shorter than other mills at the time in New England, suggesting possible quality problems during construction (in fact, one of the original cast-iron support columns was found to have an irregular cross section ߞ; evidence that the engineers on the site didn’t do their job); and third, heavy machinery used in cutting and punching textile was excessively loaded on the mill’s fourth floor on the day of the collapse.

“This produced what we call stress/load concentration, which crashed the floor slabs and led to progressive failure of the building’s structure,” says Yu.

Yu created a computer simulation of such structural failure due to impact loading to reproduce the collapse of the Pemberton Mill. His animation shows heavy machinery crashing onto the ground floor, causing the support beams and columns to fail and collapse.

“This simulation represents only a qualitative, not quantitative, analysis model since there are a lot of variables involved,” he says. “We have no information about the exact physical properties and characteristics of the construction materials used in the mill so it is difficult to predict the building’s structural behavior with great scientific accuracy.”

As for the effect of the Pemberton collapse on mill safety, Forrant says there was next to none.

“Laborers did not have any worker’s compensation at the time and many families who lost wage-earners became destitute as a result of the mill’s collapse,” he says. “No one was punished for the Pemberton disaster. It took another major tragedy ߞ; the Triangle Shirtwaist Factory fire in New York City in 1911 ߞ; to begin to create workplace safety reforms. However, it was not until 1972 that the country obtained national health and safety regulation with the creation of the Occupational Safety and Health Administration.”